There
exist two defences of duress: duress by threats and duress of circumstances. Duress of
circumstances is the most recent development in criminal law and is closely linked to duress
by threats and the defence of necessity. Duress by threat and duress of circumstances are largely governed by the same criteria thus many of the cases are authority for either type of duress. Where the defence of duress
is successfully pleaded it absolves the defendant of all
criminal liability. The rationale behind the defence of duress is
that whilst the defendant clearly has the mens rea of the crime, in
committing the crime, they are acting out of compulsion and are therefore not
exercising freedom of choice. In this respect the defence of duress
differs from most defences which seek to demonstrate the defendant lacked
the mens reafor example,intoxication, insanity and mistake. The defence of duress also differs from the defences of self-defence and prevention of crime which perhaps provide a justification for committing a crime. Duress operates to provide an excuse for
criminal behaviour. In this respect the defence of duress has often been described as a concession to human frailty. Whilst the defence of duress is a general
defence, there are some limits on its application. In particular the defence
of duress cannot be raised in crimes of murder, attempted murder or by
those who participate in killing. Recent case law suggests a narrowing in its application.

Duress by threat

Duress by threat was defined inA-G v Whelan [1993]
IEHC 1 Case
summary as being available when the accused was told to commit an
offence and was subject to:

“Threats of immediate death or
serious personal violence so great as to overbear the ordinary powers of human resistance.”

It is for the jury to decide
whether the threat was sufficiently serious to warrant the defence of duress which will
be balanced against the seriousness of the offence. The elements of the defence were more recently stated by Lord Bingham in the House of Lords decision of R v Hasan [2005] 2 WLR 709:

Where the defendant became indebted to drug dealers and is subjected to threats if they do not commit an offence, they are taken to have put themself in the position and the defence of duress is denied:

If the defendant could reasonably have obtained police protection or acted in some way to avoid the crime they would be expected to take that action rather than commit the crime. The defence of duress is therefore denied in these situations. This matter was discussed in:

Duress of circumstances differs from duress by threat in that the circumstances dictate the crime rather than a person. It may well be a person that creates the circumstances, but there is no requirement that a person specifies that a crime must be committed. Although there must still be a sufficient nexus between the threat and the crime:

The defence of duress of circumstances grew out of the inflexibility afforded in the defence of necessity. It is often referred to as necessity by another name. It will often allow a defence where the defence of necessity would deny one. The defence of duress of circumstances came about largely as a mistake in the case of R v Willer in which the defendant raised the defence of necessity. The Court of Appeal allowed his appeal and stated that he should have used the defence of duress. However, he had not been told to commit a crime, the threat came from the circumstances:

This then set a precedent which was followed in R v Conway where the Court of Appeal noted that there was no threat in R v Willer but recognised the existence of the new defence and named it duress of circumstances: